Exploratory Aim 1b. To determine if varenicline results in a greater proportion of methamphetamine dependent participants achieving methamphetamine abstinence defined as self-reported MA abstinence, confirmed via urine drug screens (all available urine drug screens are MA-metabolite free and at least one urine drug screen available per week and no more than two missed visits between urine drug screens) during the final two weeks of the study medication period (weeks 7 and 8) relative to placebo when provided in conjunction with cognitive behavioral therapy.